1. Field of the Invention
The present invention relates to an ink composition, an ink set suitable for recording an image by jetting an ink according to an ink-jet method, and an image forming method using the same.
2. Description of the Related Art
The ink-jet technique has been applied as an image recording method for recording color images in the fields of an office printer, a home printer, and the like. Ink for use in ink-jet recording has been examined to improve the rubbing resistance by blending a polymerizable monomer in an aqueous pigment ink and curing the same. For example, an ink-jet recording method is disclosed that includes applying a reaction mixture containing a reaction agent that generates an aggregate upon contact with an ink composition and a photopolymerization initiator and an ink composition containing an acrylate monomer or a resin emulsion to a recording medium, and performing printing (e.g., Japanese Patent Application Laid-Open (JP-A) No. 10-287035).
In addition, it has been examined to increase the degree of crosslinking of images to be formed to thereby increase the degree of adhesion to a recording medium. For example, active energy ray-curing type aqueous inks that contain a polymerizable monomer having a specific structure are disclosed (e.g., JP-A No. 2007-314610).
Furthermore, as a technique for improving the adhesion to a recording medium that does not absorb ink, such as plastic, the use of an ink composition containing a specific polymerizable monomer is disclosed (e.g., JP-A No. 2001-115067).
However, according to each technique described above, the ejection stability (recovery from leaving), in a case in which the ejection of an ink composition is stopped, and then after a head is left as it is for a given period of time, the ejection is re-started on an ink-jet recording device, is extremely insufficient.
According to the method disclosed in JP-A No. 10-287035, for the aqueous pigment ink in which an aqueous medium is used, the solubility of a monomer is not considered. As a result, a problem occurring when a water-soluble monomer is added cannot be avoided. Such an ink composition is problematic in that the monomer and the pigment are separated, and thus it is difficult to obtain sufficient curing properties of image are, and also in addressing a phenomenon (blocking) in which images are locally stuck and are not separated with the passage of time in a state where the image surfaces are in contact with each other. Moreover, this method is a method including bringing a reaction liquid and an ink into reaction, and fixing the ink. However, the monomer tends to separate, and thus the fixing reaction is also insufficient.
The present invention has been made in view of the above, and particularly aims to provide an ink composition that achieves an excellent effect in terms of ejection stability (recovery from leaving) even in a case in which ejection of the ink composition is stopped, and then after a head is left as it is for a given period of time, the ejection is re-started on an ink-jet recording device, and that has excellent curing properties of image and blocking resistance, an ink set, and an image forming method using the same, and an object of the present invention is to solve the above-described problems.